Method and device for receiving and treating audiosignals in surroundings affected by noise

Abstract

In order to record and to process audio signals with a good useful-signal to noise-signal ratio in acoustic noise conditions and with a good ratio between the direct sound and the reflected sound in an environment which in particular has no reverberation electrical signals produced by conversion of audio signals recorded by a predetermined microphone arrangement are processed in such a manner that, if the sound pressure levels at the microphones in the microphone arrangement are the same, electrical signals which are produced by these microphones but are of different intensity—different sensitivities of the microphones—are automatically matched, without any manual matching procedures needed to be carried out individually and separately. A microphone arrangement is based on combining the characteristics of an array of microphones with those of a method for matching the sensitivity of microphones.

Description

BACKGROUND OF THE INVENTION [0001] Previous methods and devices for recording and processing audio signals (for example speech and / or sound signals) in an environment filled with acoustic noise are based either on the use of a first-order directional microphone (gradient microphones) or on a microphone array having two or more individual microphones (for example ball microphones). In the latter case, additional digital filters are used to match the frequency responses of the microphones. [0002] Both directional microphones and microphone arrays are covered by the generic term free-field microphones, whose directivity allows the useful sound and the acoustic noise to be separated, and whose output signals are added using the “delay and sum principle”. [0003] Microphone arrays are arrangements of a number of microphones positioned physically separately, whose signals are processed such that the sensitivity of the overall arrangement is directional. The directivity results from the pro...

AI Technical Summary

Benefits of technology

[0007] An advantage of the present invention is to record and to process audio signals with a good useful-signal to noise-signal ratio in acoustic noise conditions and with a good ratio between the direct sound and the reflected sound in an environment which in particular has no reverberation.

[0008] According to the invention, there is processing of electrical signals produced by conversion of audio signals recorded by a predetermined microphone arrangement in such a manner that, if the sound pressure levels at the microphones in the microphone arrangement are the same, electrical signals which are produced by these microphones but are of different intensity—different sensitivities of the microphones—are automatically matched, that is, without any manual matching procedures needing to be carried out individually and separately.

[0009] The invention, in this case, pertains to combining the characteristics of an array of microphones with those of a method for matching the sensitivity of microphones.

[0010] Advantages of this procedure involve simple implementation in conjunction with the (optimum) result achieved in the process and, a good relationship between the complexity of the microphone arrangement (arrays) and the result.

[0011] The result which can be achieved using the present invention is considerably better than the result which can be achieved by using U.S. Pat. No. 5,463,694. This is shown in the following table:

[0012] The table shows the relationship between the “difference between the sensitivity of the microphones (delta)” and the “directivity index”Delta (dB)Directivity index (dB)08.718.428.137.847.557.266.9

Problems solved by technology

A problem that arises in the practical implementation of microphone arrays is the scatter, resulting from production tolerances, in the sensitivity and frequency response of the individual microphones used.

If these microphone characteristics differ within a microphone array, then this has a negative influence on the frequency response and the directional characteristic of the overall arrangement.

The acoustic measurement of the microphone parameters involves considerable technical complexity and results in corresponding costs for the production of microphone arrays.

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